Mississippi Turfgrass - Summer 2017 by leadingedgepubs

Summer 2017

The Mississippi Turfgrass Association Magazine

Fine-tuning pgr applications Using Growing Degree Days and Base Temperatures

Annual Bluegrass Control in Mississippi Home Lawns Plus, Mark Your Calendars! 2017 Turfgrass Research Field Day, August 22

summer 2017

Contents • The Mississippi Turfgrass Association Magazine Features

7 Save the Dates —

8 Upcoming Event —

Deep South Turf Expo, November 7–9

2017 Turfgrass Research Field Day, August 22

10 Cover Story —

Fine-Tuning PGR Applications Using Growing Degree Days and Base Temperatures

16 Lawn Care Tips — Annual Bluegrass Control in Mississippi Home Lawns

Departments

6 From the MTA President 21 Mississippi State Turf Team

22 Calendar of Events 22 Index of Advertisers

Mississippi Turfgrass is the Mississippi Turfgrass Association magazine. Subscriptions are complimentary to MTA members. The statements and opinions expressed herein are those of the individual authors and do not necessarily represent the views of the association, its staff, its board of directors, Mississippi Turfgrass, or its editors. Likewise, the appearance of advertisers, or their identification as MTA members, does not constitute an endorsement of the products or services featured in any issue of Mississippi Turfgrass. Copyright ©2017 by the Mississippi Turfgrass Association. Mississippi Turfgrass is published quarterly. Subscriptions are complimentary to members of MTA. Presorted standard postage is paid at Nashville, TN. Printed in the U.S.A. Reprints and Submissions: MTA allows reprinting of material published here. Permission requests should be directed to MTA. We are not responsible for unsolicited freelance manuscripts and photographs. Contact the managing editor for contribution information. Advertising: For display and classified advertising rates and insertions, please contact Leading Edge Communications, LLC, 206 Bridge Street, Franklin, TN 37064, (615) 790-3718, Fax (615) 794-4524.

From the mta president

Kicking off a

Erick Coomer

Strong Summer

Mississippi Turfgrass Association Box 9555 MS State, MS 39762 Office: (662) 325-0517 Fax: (662) 325-2705 www.msturfassociation.org Published by: Leading Edge Communications, LLC 206 Bridge Street Franklin, TN 37064 Office: (615) 790-3718 Fax: (615) 794-4524 info@leadingedgecommunications.com Mississippi Turfgrass Editor James D. McCurdy, Ph.D.

MTA OFFICERS

nother summer is upon us. I hope this issue of Mississippi Turfgrass finds everyone enjoying themselves and the busy workload that goes with the season. This time of year is what we all look forward to — revenue is up (hopefully), and the workday seems to fly by. Although we are all grinding away to accomplish all the goals we have for the year, we should take the necessary breaks to spend time with family and friends, so they’ll remember your name when fall comes back around. Here are few key events to look forward to:

August 22, 2017

Turfgrass Research Field Day Starkville, MS

November 7-9, 2017 Deep South Turf Expo Biloxi, MS

I’d like to welcome Dr. Eric Reasor, the newest addition to the MSU turfgrass team. Eric joins us from the University of Tennessee. His appointment is largely teaching but with a research component to develop new turfgrass cultivars. His expertise is in off-type bermudagrass and the use of plant growth regulators. His official start was July 1. Welcome, Eric! I’d also like to congratulate Mr. Will Arnett. This spring, Will joined East Mississippi Community College as superintendent at Lion Hills Golf Course and adjunct instructor. I know we’re all happy to have him sharing his experience with aspiring turf professionals. Again, I hope everyone is enjoying the summer. See you at Field Day and Deep South Turf Expo!

Erick Coomer 2017 MTA President

President Erick Coomer The Bridges Golf Course (228) 860-5292 Vice President David Leon Turf & Aquatic Specialties, LLC (601) 529-2458 Secretary/Treasurer Wayne Philley Mississippi State University (662) 325-2728 Past President Paul Welborn Lawn and Pest Solutions (662) 316-1347 Administrative Secretary Linda Wells Mississippi State University Box 9555 MS State, MS 39762 Office: (662) 325-0517 Cell: (662) 769-7558 lmw218@pss.msstate.edu

Directors

Jay Coalter Castlewoods Country Club (601) 317-1641 Dan Crumpton Oasis Sod Farms (662) 621-2040 Keair Edwards City of Gulfport (228) 861-5641 Al Osteen (601) 214-9907 Jeremy Tate Tate’s Turf LLC (662) 209-0023 Reuben Wedgeworth Agri-AFC Purvis, MS (601) 498-0750

6 • Mississippi Turfgrass • Summer 2017

Save the dates!

It’s Coming!

So Be Sure to Mark Your Calendar and Save These Dates! NOVEMBER 7–9

Deep South Turf Expo Mississippi Coast Coliseum & Conference Center Biloxi, MS

The Mississippi Turfgrass Association Magazine • 7

Upcoming Event

2017

T urfgrass

researc H Field Day

August 22 | Starkville, MS 8:00 a.m. 8:45 a.m. 9:00 a.m.

Registration with coffee & pastries

for attendees and vendors in the exhibit area.

Welcome to the 2017 MSU Turfgrass Research Field Day

Dr. Jay McCurdy, Assistant Professor, Extension Turfgrass Specialist

Rotation sessions

Attendees will be placed in groups that visit each station.

Educational Station 1

Educational Station 2

Educational Station 3

Educational Station 4

Educational Station 5

Turfgrass Breeding and Selection Mr. Wayne Philley

Weed Management Strategies Dr. Jay McCurdy

Cultural Practices that Enhance Athletic Field Playability Dr. Barry Stewart

Plant Growth Regulators for Bermudagrass Sports Surfaces Dr. Eric Reasor

Disease Management Dr. Maria Tomaso Peterson

11:00 a.m.

Vendor expo, door prizes and more.

12:00 p.m.

Lunch provided by Gold Sponsors!

1:00 p.m.

Concurrent sessions. Attendee’s choice.

visit: blogs.msucares.com/turfgrass #MSUTurfFieldDay17

Landscape and Horticulture

Sod Production

Golf Course

Plants for the Landscape Dr. Geoff Denny

Grow-In, Sod Strength and Herbicide Selection Mr. Erick Begitschke

Preemergence Herbicides for Native Grass Establishment Mr. Michael Richard

MSU Turfgrass Field Day Registration Due August 1, 2017

Registration Turf or Ornamental Professional (on-site registration is $50)

$40

Shirt Size...................................................................................................................

Extension agent, faculty, staff, or student

Free with preregistration

Donation to the MSU Turf Endowment

$..............

Name........................................................................................................................ Business................................................................................................................... Address..................................................................................................................... City............................................................ State......................... Zip......................... County....................................................................................................................... Email........................................................................................................................

Help us sustain 50 more years of MSU Turf Endowment

Total $..............

Register and pay online at www.pss.msstate.edu/workshops/turf2017, or complete the registration form and mail with your check made payable to Mississippi State University. Mail form with payment to: Jay McCurdy • P.O. Box 9555 • Mississippi State, MS 39762 Mississippi pesticide applicator recertification (categories 3 and 10) and MSU Extension in-service training will be offered. Mississippi State University is an equal opportunity institution.

The Mississippi Turfgrass Association Magazine â&#x20AC;˘ 9

Cover Story

Fine-Tuning PGR Applications Using Growing Degree Days and Base Temperatures By Barry Stewart, Ph.D., Associate Professor, Mississippi State University, and Ethan Flournoy, Assistant Superintendent, Deerfield Golf Club

very year in my plant science course, we start by talking about some of the factors needed to grow a plant. Sunlight and water are the two at the top of the list. Next someone will mention soil, and it never fails that hydroponics are brought up. The plants can grow in soil or hydroponics as long as the right nutrients are provided along with support so that the plants can present their leaves to the

10 • Mississippi Turfgrass • Summer 2017

sun. Eventually a student thinks of air being needed for CO2 and O2. We then begin to look for that final factor. The one that does not immediately come to mind is the correct temperature. Outside of the winter months, we tend to forget about the profound effect temperature has on plants and their physiology. In the past two years, we have undertaken several experiments at Mississippi

State University to examine the effects of temperature on warm-season grasses, as well as the effect of temperature on plant growth regulator (PGR) response. One of the ways agronomists quantify temperature is by modeling heat accumulation, often termed “growing degree days” or GDDs. The GDD unit is one of the most frequently modeled indicator of heat accumulation. GDDs are used by agriculturalists

to predict when distinct growth stages of plants will occur, such as days until flowering or days until maturity (Miller et al., 2001). GDDs are defined by McMaster and Wilhelm (1997) as the amount of heat energy received by the plant for a given time period. Growing degree days are calculated by averaging the daily maximum and minimum air temperature and then subtracting the base temperature for the plant being grown. Base temperature is the temperature at which plant processes do not progress. In the turfgrass industry, GDD models have gained favor for optimizing plant growth regulator applications (such as Green Keeper App and others), but they have historically been used to predict plant growth and development, such as seedhead production, disease outbreak, weed emergence, etc. By using GDD models, input timings can be based more on the needs of the plant as opposed to a calendar-based approach. This is not a new idea, but the prediction of base temperatures for different grasses has been limited to only a few studies. A critical factor in using any heat model is the determination of an accurate base temperature (Arnold, 1959). If a base temperature used in the calculation of GDD is off by 2°C, then the total accumulated GDD can vary by as much as two calendar weeks (Unruh et al., 1996). It is very important to note that base temperature can vary between species and growth stages (Wang, 1960). Base temperature may even vary between cultivars and biotypes, which makes it all the more important for predicting plant growth regulator (PGR) applications, so as not to over-regulate and also to help optimize turf health/performance. Research conducted at Mississippi State University examines the effects of temperature on warm-season grasses as well as the effect of temperature on PGR response. The Soil-Plant-AtmosphereResearch Facility at MSU is ideal for this type of research (Photo 1). Its Plexiglas® chambers allow approximately 95% of photosynthetically active radiation to pass through, a notable improvement

Photo

The SPAR Soil Plant Atmosphere Research Units on MSU’s North Farm.

from previous research conducted in artificially lit growth chambers. Air circulated within the SPAR chambers can be cooled and/or heated to within a fraction of a degree of the desired temperature.

Bermudagrass base temperature

We determined the base temperature for the following hybrid bermudagrasses: ‘MSB-285’ (experimental cultivar), ‘Latitude 36’, ‘TifEagle’ and ‘Tifway’ (Photo 2). Bermudagrass was grown in 3:1 sand to soil mix (87% sand, 2% clay and 11% silt), with gravel at the bottom of each pot. Each pot had a hole drilled in the bottom to allow for drainage. Irrigation was provided three times per day using a half-strength Hoagland’s nutrient solution. Day- and night-time temperatures (in Celsius) for the different chambers were 20°C/12°C, 25°C/17°C, 30°C/22°C, 35°C/27°C and 40°C /32°C.

Data collection

Clipping yield was collected every three days, using scissors and a guard cut to desired height. The collected clippings were dried and then weighed. TifEagle was maintained at 0.5" while Latitude 36, MSB-285 and Tifway were maintained at 0.75".

Base temperatures

For GDD models in turf, the Celsius temperature scale is used. This makes work in cool-season grasses easy since the base temperature is assumed to be 0°C. So, the daily GDD that is equal to the average daily temperature is simply the daily high + the daily low divided by 2. For warm-season grasses, we know that some impairment in growth happens around 10°C (50°F). Growing degree day models for corn, another warm-season grass, have been well researched, and a base temperature of 50°F is used as well, so 10°C is probably a good guess at the base temperature for bermudagrass. After conducting the experiment in the SPAR units, we generated graphs for all the bermuda cultivars tested. The graph for Tifway will be used as an example (Figure 1). As the temperature decreases to near the base temperature, the data becomes somewhat unreliable. To overcome this, temperatures are chosen near but above the likely base temperature, and then regression modeling is used to estimate the base temperature. In the Tifway example, it appears that 11°C is the base temperature. These data are preliminary since our total analysis is not finished, but at The Mississippi Turfgrass Association Magazine • 11

Cover Story • Continued

The clipping yield by temperature curve for Tifway bermudagrass. The best fit curve crosses the X-axis near 11°C in this example, and that would represent the base temperature.

Clipping yield, g m-2

Tifway

y = -66.4318 + 6.5375x - 0.1014x2; r2 =0.58

Figure

10 10

Temperature, ˚C Ethan Flournoy and Wayne Philley record data from the SPAR unit experiment.

Photo

12 • Mississippi Turfgrass • Summer 2017

this point, we may conclude that the base temperature for bermudagrass is just slightly higher than 10°C. From this curve, we can also calculate an optimal temperature for growth; that appears to be 27°C (80.6°F) for this example. We hope to be able to determine a coefficient for growth potential for each of the bermudagrasses tested. This may allow the prediction of clipping yields as temperatures change and also calculate how well our PGRs are regulating growth. When growth regulation declines and actual yields begin to match predicted yields for a given temperature, reapplication of a PGR would be warranted. Once the base temperature is calculated, a separate experiment must be conducted to determine the reapplication interval. For creeping bentgrass putting greens, Kreuser (2015) has determined the reapplication interval of Primo (Trinexapac-ethyl) is 200 GDDs. This summer, Dr. Eric Reasor (a new member of the turf team at Mississippi State) will be conducting experiments to determine the reapplication intervals of several PGRs on ultradwarf bermudagrasses. Given that Primo has a greater rate of growth suppression in bermudagrass greens, it may be a logical conclusion that the reapplication will be longer than 200 GDDs. Reapplication varies drastically with what base temperature you decide to use. According to work conducted by Ethan Flournoy (Flournoy, 2017) using temperatures from 2016, if Primo was applied on March 1 using a 10°C base temperature, 300 GDDs would be accumulated on April 22. On the other hand, if a base temperature of 13°C is used, 300 GDD would not be reached until May 10, quite a difference! As another example, if Primo were applied on July 1, 2016, with a 10°C base temperature, 300 GDDs would be reached on July 17. With a base temperature of 13°C, 300 GDDs would be applied on July 20. You can tell two things from these examples. One is that during cooler temperatures, a reapplication interval based upon time rather than GDD

Cover Story • Continued

models means it’s possible to overand/or under-regulate the turf. Another thing that you should notice is that the error in base temperatures (the difference between 10°C and 13°C) can make a huge difference in predicting reapplication intervals in cooler temperatures. This is why, during cooler parts

of the year, we should apply PGRs less frequently than a calendar-based schedule, such as application every 14 days. We also should apply less product during cooler parts of the year due to the decreased metabolism of the plant. During hot parts of the summer, the application interval using

GDD models may lead to PGRs being applied more frequently. One way to track GDD is by using the Greenkeeper App, available for free from the University of Nebraska. This tool will be quite valuable for those looking to fine-tune their PGR applications. As these models evolve, the area of the growth curve beyond the optimal growth temperature will be examined, and the effects of “heat stress” will be quantified. The effects of natural rainfall and sunlight intensity may someday also be included, as may the effects of mowing and clipping removal. This will be an exciting area of research for a number of years, and the results should lead to more efficient use of PGRs by superintendents and more consistent playing conditions for the users of golf courses and athletic fields. v

References

Arnold, C. Y. 1959. The determination and significance of base temperature in a linear heat unit system. Proc. Amer. Soc. Hort. Sci. 74:430-445. Flournoy, E. T. 2017. Temperature effects on warm and cool season grass species and cultivars. MS Thesis, Mississippi State University. Kreuser, W. C. 2015. Effective Use of Plant Growth Regulators on Golf Putting Greens. USGA Green Section Record. Vol. 53 (7) April 3, 2015. McMaster, G.S., and W.W. Wilhelm. 1997. Growing degree-days: one equation, two interpretations. Ag and For. Meteo. 87:291 – 300. Miller, P., W. Lanier, and S. Brandt, 2001. Using growing degree days to predict plant stages. Ag/Extension Communications Coordinator, Communications Services, Montana State UniversityBozeman, Bozeman, MO. Unruh, J.B., R.E. Gaussoin, and S.C. Wiest. 1996. Basal growth of temperatures and growth rate constants of warm-season turfgrass species. Crop Sci. 36:997-999. Wang, J.Y. 1960. A critique of the heat unit approach to plant response studies. Ecology 41(4):785-790. 14 • Mississippi Turfgrass • Summer 2017

Lawn Care Tips

Annual Bluegrass Control

in Mississippi Home L By Michael Richard, Extension Associate, and Jay McCurdy, Ph.D., Assistant Professor, Mississippi State University

nnual bluegrass (Poa annua), commonly called “Poa,” is a problematic winter annual weed in residential turf. It has a bunch-type growth habit with light green leaves that have a distinct boat-shaped tip. Annual bluegrass is a prolific seed producer and is commonly identified by its unsightly greenish-white seedheads. Each plant is capable of producing hundreds of seeds that can lay dormant in the soil for years before becoming a plant. Annual bluegrass can withstand mowing heights common in residential lawns and grows just about anywhere, including sidewalks, but it prefers areas with moist or compacted soils. Contrary to its name, both annual and perennial biotypes of Poa are present in Mississippi. The annual type tends to be more prevalent in lawns. These attributes make annual bluegrass a formidable 16 • Mississippi Turfgrass • Summer 2017

weed in residential turf. Annual bluegrass seeds germinate in late summer and early fall when soil temperatures drop below approximately 70°F. During the fall, seedlings grow vegetatively, and the plant produces seeds from late winter through early summer. Several flushes of germination are common throughout fall, winter and spring. Heat and dry conditions during the summer usually lead to plant death. Controlling annual bluegrass is possible, but it takes an integrated approach. Cultural practices — such as proper mowing, fertility and irrigation — are important, but they may not be completely successful.

Cultural control

As is the case with most weeds, a healthy, dense turf is the best defense

against annual bluegrass infestations in home lawns. Sound agronomic practices — including proper soil pH and fertilization, deep infrequent watering, proper mowing and insect and disease management — will promote a healthier turf to compete with annual bluegrass. Weak and thin turf is the prime place for weeds to establish. Annual bluegrass thrives in wet areas, so improving soil drainage can aid in turf competition. Excessive watering in the fall often leads to weakened stands of turf due to disease pressure and weakened roots, all of which lead to annual bluegrass invasion. Soil compaction can also exacerbate the problem. Core aerification during the summer will help alleviate compaction to promote turfgrass growth. Aerification is a disruptive process; therefore, it is necessary to give warm-

Continued

•

Cover Story

Annual bluegrass (Poa annua) seed head and “boat shaped” leaf tip.

Lawns season grasses enough growing time to recuperate. It is not recommended to aerify lawns in the spring or fall when turf is not actively growing. Eliminate nitrogen fertilization during late fall and on dormant warmseason turfgrass. Late fertilization will unnecessarily promote annual bluegrass growth and expose warm-season grasses to winter injury. Applications of nitrogen fertilizer are not recommended in Mississippi after mid-September. Mowing heights vary among species (Table 1). Raising the mowing height in the fall can increase the competitiveness of warm-season grasses. Scalping the turf opens the canopy, which can lead to infestation by winter annual weeds (including annual bluegrass). To prevent scalping, never remove more than one third of the leaf blade at each mowing. Collecting clippings when annual blue-

Raising mowing height in the fall can aid in reducing annual bluegrass infestation. Left: Bermudagrass mown at 0.75” • Right: Bermudagrass mown at 1.5”

grass is seeding may be useful to reduce the spread of seed.

Chemical control

Where cultural practices fall short, herbicides are often needed. There are several herbicide options and strategies for controlling annual bluegrass.

Preemergence weed control

Preemergence herbicides are applied prior to annual bluegrass germination, so application timing is critical for proper control. Annual bluegrass germination varies from year to year, but herbicide applications should be applied in late summer/early fall before annual bluegrass germinates. Applying herbicides early rather than late is recommended. This may mean applications as early as midAugust in northern Mississippi and as

late as October 1 in coastal Mississippi. Preemergence herbicides need to be incorporated into the soil after application via irrigation or rainfall. Most preemergence herbicides can be applied to warm-season turfgrasses, although some do inhibit the root growth of desired turfgrass. Some are safer than others, but safety is rate dependent. Stoloniferous grasses (centipedegrass and St. Augustinegrass) seem to be more prone to injury by these herbicides; thus, care should be taken when making an application. Using lower labeled rates is a best practice for sensitive grasses. Fall applications of commonly used preemergence herbicides — such as pendimethalin, prodiamine, benefin, trifluralin, dithiopyr and oryzalin, as well as combinations — may effectively control annual bluegrass. These mitotic The Mississippi Turfgrass Association Magazine • 17

lawn care tips • Continued inhibiting herbicides inhibit cell division in the roots of young plants and are available in a variety of trade names and formulations. However, the exclusive use of mitotic inhibiting herbicides has led to resistant biotypes of annual bluegrass in the Southeast. Rotating the herbicide mode of action is recommended to reduce resistance and allow for continued use of these preemergence herbicides.

Table 1. Recommended mowing heights.

Turfgrass

Inches

Bermudagrass

1/2" to 1-1/2"

St. Augustinegrass

2-1/2" to 3"

Centipededgrass

1-1/2" to 2"

Zoysiagrass

1" to 1-1/2"

Carpetgrass

1" to 2"

Bensulide (a lipid synthesis inhibitor) and indaziflam (a cellulose biosynthesis inhibitor) are options if resistance to mitotic inhibiting herbicides is confirmed. Only use indaziflam in established lawns free of pests, disease or stress. Once again, these herbicides lack postemergence activity, so timing is critical to proper efficacy.

broadleaf winter annual weeds. Generally, these herbicides can be safely applied to bermudagrass, carpetgrass, centipedegrass, St. Augustinegrass and zoysiagrass. Atrazine should be applied only to dormant bermudagrass unless injury can be tolerated. Simazine may be safely applied to actively growing warm-season grasses. Continuous use of these two products has led to annual bluegrass that is resistant to PSII inhibiting herbicide, so the herbicides’ effectiveness is somewhat limited when these herbicides are applied alone. Options outside these two herbicides are limited. Flumioxazin, a protoporphyrinogen oxidase inhibiting herbicide, can be applied to dormant bermudagrass to control annual bluegrass. Applications to actively growing turfgrass may cause unacceptable injury.

Pre- and postemergence weed control Herbicides with pre- and postemergence activity control young bluegrass seedlings and prevent the success of germinating seeds. These herbicides work well as a late fall/early winter cleanup application. The two most common pre/post herbicides in Mississippi are atrazine and simazine, both of which are photosystem II inhibiting herbicides. These PSII inhibiting herbicides also control a broad spectrum of other

Mode-of-action and classification of common herbicides for annual bluegrass control. Mode of action is listed according to the Weed

Table 2. Science Society of America (WSSA) and the Herbicide Resistance Action Committee (HRAC).

Timing

Mode-of-Action

WSSA Group

HRAC Group

Common Name

Trade Name

Pre